GRB 221009A/Swift J1913.1+1946: Assy optical afterglow observation

We observed GRB 221009A/Swift J1913.1+1946 (Dichiara et al., GCN 32632; Kennea and Williams, GCN 32635; Veres et al., GCN 32636; Bissaldi et al., GCN 32636; Svinkin et al., GCN 32641; Piano et al., GCN 32657; Pillera et al., GCN 32658; Gotz et al., GCN 32660; Frederiks et al., GCN 32668) with AZT-20 telescope of Assy-Turgen observatory starting on 2022-10-10 (UT) 17:12:51. The observations were carried out sequentially with three images for 30 seconds, in each filter. In stacked images we clearly detect the optical afterglow (e.g. Dichiara et al., GCN 32632; Lipunov et al., GCN 32634; Perley GCN 32638; Hu et al., GCN 32644; Belkin et al., GCN 32645; Kuin et al., GCN 32656). Preliminary photometry of the afterglow is following Date UT start t-T0 Exp. Filter OT Err. UL(3sigma) (mid, days) (s) 2022-10-10 17:12:51 n/a 18*30 r' 18.64 0.03 20.8 2022-10-10 17:14:51 n/a 15*30 g' 20.53 0.11 21.1 2022-10-10 17:21:07 n/a 15*30 i' 17.58 0.01 20.7 2022-10-10 17:24:16 n/a 15*30 z' 16.87 0.05 19.8 The photometry is based on the nearby PS1 stars.